Decontamination process utilizing alkali-sensitive coatings



t 3,063,873 DECONTAMINATION PROCESS UTILIZING ALKALI-SENSITIVE COATINGS John R. Saroyan, 1320 Carl Ave., Vallejo, Calif. No Drawing. Filed Feb. 8, 1960, Ser. No. 7,494-

, 5 Claimsn (Cl. 1344) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or erefor.

The present inventionrelatemto a decontamination. process and, more particularly, to one employing either alkali-solution-removable or hot-water-removable protective coatings.

The protection of surfaces from contaminants has been a continual problem which has received an upsurge of attention with the advent of atomic weapons and the resulting danger from radioactive particles. In addition to the more notorious radioactive fallout contamination,

contaminating substances such as dirt, grit, tar, paint,

of thecontaminant sandblasting or some other equally States Patent 0 difllcult and expensive procedure then has been resorted to.

According to the present invention, the surface-to-beprotected is coated prior {to exposure to contamination with a protective coating composition lwhich forms upon the surface a dry film of high durability and high weatheringcapability. The nature of the coating composition employed is such that the resulting film has excellent wear and weathering-properties and is at the same time hot-water-removable'. -After the coated surface has been exposed to contamination it is then subjected to hot water (fresh, brackish, or seawater) under p'ressure. The coating (dry film), now contaminated, under the action of the hot water or steam under pressure loses its' adhesive capability and is stripped from the surface. As an application example, such a composition would be applied 1 to the skin of a naval vessel to' serve thereon as a durable protective coating. After nuclear attack this coating would be washed away by the steam of hot water carryingwith it the radioactive particles embedded therein, thereby freeing the ship from contamination.

To meet situations where a severe degree of contamination is to be encountered the invention embraces the use of easily-removed undercoatings to supplement the aforementioned top protective coating. The undercoating serves as an additional barrier between the contaminants and the 'to-be-protected surface. As with the top protective coating, this undercoating is removed, after conlamination, front the surface it covers and carries along with it any contaminants 'which havepenetrat'ed past the top coating. In one embodiment an alkali-removable undercoating is used. To illustrate use of the hot-waterremovable top coating and an alkali-removable under- 2 coating consider a shipv at sea trapped in radioactive fallout. By subjecting the exposed surfaces-of the ship with hot seawater under pressure somewhere from -95%015 the radioactive particles are removed alongwith the hotwater-removable top coating in a process of tactical de contamination. After the ship has returned to shipyard the alkali-sensitive undercoating along with the remaining contaminants is removed by the application of a mild. alkali solution. In another embodiment a water-sensitive undercoating is employed. This water-sens'itive-undercoating may vary considerably in adhesive and cohesive properties from the top protective coating. This watersensitive undercoating is removed, after contamination exposure, at the same'time as the top coating'under the action of the pressured hot water or steam and, in fact,

usually expedites the removal of the top coating- The invention further contemplates the use ofan alkali- 7 sensitive coating as the sole coating to be applied to the I to-be-protected surfaces. Such a coating may be removed in whole or in part to meet various degrees of contamination.

An object of the present invention is to provide a quick, facile, and economical method for freeing surfaces from contaminants, including radioactive contaminants.

A further object is to provide a decontamlnationprocess which, as one of its steps, provides a normal, durable protective covering for surfaces involved.

Another object is to provide a decontamination process capable of freeing surfaces from a severe degree of con- 30- tamination. 4 An additional objectis to provide a coating composition which serves as a protective coating under normal...

operating conditions and which easily can be sloughed '1 oh after contamination to free the coated surface of con-:

taminants.

A further object is to provide a protective coating composition whose dry film can be controllably and easily removed in whole or to a selected fraction of its original I thickness. A

Still another objectisv to provide a paint system of coatings and undercoatings which join to give protective coating to a surface under normal operating conditions and which can be sloughed ofi after exposure to severe contamination to leave the surface contamination-free.

Other objects and many ofthe attendant advantages of this invention readily will be appreciated by reference to the following detailed description. i

The basic coating composition of the invention comprises essentially a high polymer plastic of either theelastomeric type or the thermoplastic type, or a combination of both, formulated with a water-sensitive adhesion modifier. The-polymer plastic is substantially water-insoluble and may possess various degrees of cohesive or adhesive properties. The elastomeric type commonly possesses excellent cohesive properties and is limited to poor adhesive properties; the thermoplastic types possess a range of various degrees of cohesive and adhesive prop erties. This water-sensitive adhesion modifier must'be of a type capable of at least maintaining the adhesive property of the particular plastic and, preferably, of increasing this adhesive property. The water sensitive adhesion modifier is preferably, butnot necessarily, a filmforming material.

Among suitable high polymer elastomeric materials are.

a l r I i 3,063,873 Patented Nov. 13, 1962 ing:

the natural and synthetic rubbers. Some of the synthetic rubbers are: styrene-butadiene co-polymers (Buna S or GR-S), the chlorobutadiene polymers (neoprene or GR- M), the butadiene-acrylonitrile polymers (Buna N or GR-N), iso-butylene copolymers (s-Polymers), butyl rubber or GR-I, polyisobutylene (Vistanex) and polysulfide rubbers ('lhiokol).

Among suitable polymer thermoplastics are the followthe bitumins vinyls, polystyrene, polyethylene, acrylics and silicones. Among the vinyls are included: vinylidene chloride, polyvinyl butyral, vinyl chloride copolymers, polyvinyl chloride and polyvinyl acetate. Other appropriate thermoplastics include celluloses, such as ethyl cellulose, benzyl cellulose, cellulose acetate, cellulose' acetate butyrate, and polyamides, alkyds and glyptals.

The water-sensitive adhesion modifier, sometimes hereinafter referred to as an adhesion modifier" may include as a broad class a hydrophilic film-forming material which in waterborne systems embraces latices and water emulsions and which is known as a thickener or protective colloid. Usually this type of material promotes adhesion at ambient conditions and may further be described as a material which shows physical change in the manner of film deficiency when subjected to hot water up to 212 F. under pressure. Some typical examples of suitable water-sensitive adhesion modifiers are: polyamide 115 (General Mills: a reaction product of dimerized and trimerized linolenic and linolenic acids with ethylene diamine), hide glue, bone glue, gelatin, sodium alginate, gum arabic ammonium caseinate, sodium carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose, sodium polyacrylate, polyethylene glycol, carbowax polyethylene glycol (Union Carbide and Carbon Company), Santicizer 9 (Monsanto: mixture of ortho and para toluene sulfonamides), benzoic acid, acetanilide, diethylene glycol stearate, sodium stearate, polyvinyl methyl ether, aryl and alkyl sulfonates, glyceryl esters such as glyceryl monostearate and glyceryl mono laurate, glycol fatty acid esters such as ethylene glycol mono laurate and diethylene glycol stearate, polyethylene glycol fatty acid esters such as carbowax 4000 mono laurate and polyethylene glycol distearate and other hydrophilic materials commonly classed as wetting agents or emulsifiers such as fatty acid amines or derivatives and alkali 4 fatty acid soaps. Although not typically film formers, certain alkalimaterials, such as sodium or potassium hydroxide, have also been utilized. The preferred type of water-sensitive adhesion modifier is the film-forming type although the non-film-forming types can be utilized under certain non-critical conditions.

The sought-for goal in the formulation of the high polymer plastic with the water-sensitive adhesion modifier is the production of a coating which is sutficiently cohesive and adhesive to provide adequate protective covering and which at the same time is easily removed by the application of hot water or steam under pressure. When a high polymer plastic possessing poor or limited adhesion, and unmodified, is applied as ordinary paint over -typical surfaces, such as metal surfaces, painted or unpainted, glass, wood, concrete, asphalt, rubber, etc., it will show loss of adhesion in a relatively short time as evidenced by peeling. Commonly, when increments of water-sensitive adhesion modifiers are added to such a plastic of low adhesive properties, the adhesion characteristic of the resulting composition increases, each addition of adhesion modifier promoting up to a point the adhesive properties of the dry film of the composition. Generally, as the value of adhesion is increased, the value of cohesion decreases. The value of cohesion, however, does not decrease to the point that an unsatisfactory film will result. Thus, the addition of water sensitive adhesion modifier to the high polymer plastic produces a composition wherein adhesion is improved and the film therefrom still retains good cohesive characteristics.

7 ing and the contaminants it contains.

5 tion to another.

In the method employed herein the above-described composition is applied to the surface, which, it is anticipated, may later be subjected to contamination, and on this action is slow and the net durability of the coating is retained for extended periods of months. After the'coated surface has been subjected to contamination hot water or steam under pressure is applied to the dry film of the composition. The adhesion modifier reacts to the hot-water or steam to become mobile by dissolving, dispersing, or swelling, simultaneously lowering the adhesion of the entire film. Then the impact of the water or steam under pressure ruptures the film and separatesthe coating from the surface with subsequent complete removal of the coat- The rate of removal of the film is proportional to the rapidity with which the adhesion modifier employed is dissolved, swollen, or dispersed by the pressured hot water or steam.

When reference is made to the make-up of the coating V composition it is to be understood that the constituents of the dry film are of primary significance. hand, the composition of the wet film may vary, particularly in relation to the addition of solventsto render the composition applicable to the purpose at hand. It is obvious that, if a solvent paint is too thick to apply, adding some solvent will render it more applicable; the composition of the dry film will not have been altered thereby.

It is obvious to one skilled in the art that certain modifications in composition can be made to produce a given coating composition in three different forms or types: namely as a hot melt, solvent system, or waterborne system. Examples are:

On the other Parts by weight Example 1 Example 2 (1) nor MELT svs'rEM Ethyl cellulose N-14 (Hercules) 30 Polyami'le (General Mills) 30 70 (A- 5 stabilizer) (carbide chemicals-epoxy stabilizer). (l) (1) (Doenax, antioxidant) (may be added to prevent ltscoloriug) Example 3 Example 4 (2) SOLVENT sYs'rEn Dry film:

Ethyl cellulose (N-H) 70 30 Polynmlde 1X5 30 70 Wet film:

Ethyl cellulose sol. 15% in xylene 466 200 Polyamlde 115, 20% in xylene 350 (3) WATERBORNE SYSTEM Example 5 Example 6 Ethyl cellulose N-14 70 30 Polynmi'le 111...-.. 30 70 Ammonium caseinate, 16% sol l836 18- 36 'In'ethanolamine oleate 3-9 3-9 Water 200-400 200-400 The above listedformulations based on equal dry film thickness should produce reasonably similar films of a representative composition.

Application techniques may vary from one formula- For example, the hot melt formulation of Example 2 is viscous and best can be applied by troweling or by using high-pressure spray equipment.

However, if the amount of ethyl cellulose is reduced and replaced by more water-sensitive adhesion modifier, as

70 shown by Example 3, the viscosity is lowered and appli- 7 physical properties included:

Example 7 Example 8 Example 9 Ethyl cellulose N14 60 33 33. Santiclzer 9. 50 66 33. Castor wax (polym- 33.

crized castor oil- Baker. Stearic acid Polyamide 115 Film Sogn fiexi- Hard Flexible. l y.

Viscosity Very viscous. Lower than Lower than Application 'Irowel with Can tro\vel.. Spray with dilheulty. difficulty. Adhesion Falrlygood-.. Feir....'. Fair.

Example 10 Example 11 Example 12 Ethyl cellulose N14.. 25 50 33. Santicizer 9 25 Castor wax (polym- 25 erized castor oil- .Bakers). Stearic acid 25 Polyamide 115 50 66. Film Flexible Some flexi- Hard.

bility. Viscosity Lowest Very viscus. Lower than Application"-.. Can spray.-. Trowcl with Can trowel.

- diluculty. Adhesion Fair Fairly good-.- Fair.

It is obvious that all of the above melt coating compositions also can be formulated as solvent systems or waterborne systems as known to the art and as illustrated by Table 1 Example 13 Example 14 Example 15 Formula-Dry film:

Ethyl cellulose, N-14- 100 80. SanticizerQ O 20.

Formula-Wet film:

Ethvl cellulose 501. 666 533.

15% in xylene.

Santicizer 9 sol. 20% 0 100.

in Cellosolve.

Exposure results:

Adhesion---" Poor Fair. Cohesion. Exccllent. Very good. Dry film Tough. Alittle flexible. Condition.. Peeling Some peeling. Approximate pounds Less than 1.. About 1.

of pull required to strip a 1" pulling piece.

Example 16 Example 17 Example 18 Formula-Dry film:

Ethyl cellulose, N-14. 50. Santicizer 9 L0 50. Formula-Wet film:

Ethyl cellulose sol. 383.

15%in xylene. Santicizer 9 sol. 20% 250.

in Cellosolve. Exposure results: I

dhesion Good Very good... Excellent Cohesion ---do-. Fairly good. air.

Flexible. Flexiblc....'. Hard; No peeling. No peeling No peeling; Approximate pounds About 3-5..- About 35... About -6.

of pull required" to strip a 1" pulling piece.

' long periods of exposure are anticipated.

It is obvious that the coating composition of the inventionshould adhere permanently to the surface to applied until such time as the contaminant.

which it is has been planted and removal of the contaminant is desired.

As previously stated, this invention relates-to the decontamination of surfaces by the complete removal of a previously-applied protective coating by playing hot water or steam, under pressure, over saidsurfaees. Accordingly, the removal rate" is an important'characteristic of the given composition. To test the removal rates of given compositions an automatic traveling device housing a specially arranged jet of hot water at a predetermined temperature and pressure, at a given angle of impact, and at a predetermined distance from panels coated with the individual compositions was sped past each part at a given uniform speed. Removal tests conducted on panels coated with compositions of Examplcs 17 and 18 after 6 Weeks ofoutdoor exposure,

for example, showed the following results (removal of the coating is noted in square inches per pass):

Table 2 Example 17 Example 18 Water pressure (lbs/sq. 1n.)-.--'.--- 1 185 100 185 Water temperature F.) I 170 170 170 170 Sq. inches removal per pass 2- 10 0 1 moved than Example 18 coating composition. Hence, if f the requirements were such in this particular series of coating compositions that fast removal were required, Example 16 or 17 coating compositions would be used in preference to Example 18 coatingcomposition. Using adhesion modifiers other than Santicizer 9 faster removal rates were obtained as indicated by the following removal test results. (Formulas are all by parts by weight.)

. Table 3 Example Example 19 20 Formule-Dry film:

Benzoic acid Aeetanilide. Ethyl cellulose, N-14 Polyamicle 11 5 Formula-Wet film:

Benzoic acid sol. 20% in Cellosolve- Aeetanilide sol. 20% in Cellosnlve. Ethyl cellulose N-14 sol. 15% in xylene Polyamide 115, 20% in'xylpnp Removal tests-Formula:

Water pressure (lbs/sq. in.)--.'.-- Water temperature F)... Sq. inches removed per pass Example 22 It can clearly be seen that the removal rates of the dry film' of the coating composition shown in Table 3 are greater than the removal rates for the type of formulas shown in Table 1.

By varying the water sensitive adhesion modifier as to the hot water sensitivity property, various rates of removal can be effected. The following coating compositions of the invention given in Table 4 showed in general very fast removal rates.

It has bcenfound that the removal rate is suificiently rapid to be practical only if a minimum of 10% by weight of water-sensitive adhesion modifier is used, this 10% being figuredon the total weight of the film-forming constituents of the dry film of this composition.

There also appears to be a lower limit to the quantity of high polymer plastic required for a satisfactory composition, this amount being about 10% of the total weight of the film-forming constituents of the dry film of the composition.

The invention contemplates the use of supplementary materials in addition to the high polymer plastic and the water-sensitive adhesion modifier. These supplementary materials usually are economical and their use in combination with the high polymer plastic and the adhesion modifier would greatly reduce costs and yet not seriously alter the required film characteristics of adhesion and cohesion. Such supplementary materials usually are water-insoluble and comprise natural and synthetic resin, vegetable, mineral and petroleum wax, synthetic wax, metallic soap, plasticizer or fatty acid. Said supplementary materials may perform certain functions such as, for example, reducing the viscosity of a hot melt composition. As a specific example, the stearic acid and castor wax of Example 10 greatly reduce the viscosity of the molten coating composition thus permitting ease of application. The amount of supplementary materials used can be varied up to about 60% by weight based on the film forming constituents of the dry film of the coating composition. The basic composition may be loaded with a variety of pigments.

The following are further representative examples of the invention along with the mixing processes involved:

HOT MELT Example 31 Santicizer 9 (Monsanto) 25 Stearic acid 25 Glyceryl monostearate (Aldo 33 Glyco Co.) 25 Ethyl cellulose (N-l4, Hercules) 25 Prcess.Heat Santicizer 9, stearic acid and glyceryl monostearate together and gain 280" F.. Slowly with agitation sprinkle in ethyl cellulose. Continue to agitate until ethyl cellulose is dispersed and gain 300 F. and oil fire.

Process.-Heat Polyamide to about 275 F. Sprinkle in ethyl cellulose and agitate until dispersed. Gain 300 F. and off fire.

Example 33 Ethyl cellulose N-l 20.

Polyvinyl methyl ether 40 80.

Antioxidant and heat stabilizer may be added Very viscous. Fluid.

1% by weight Deenox and A-5.

Process-Heat polyvinyl ether to 275 F. Sprinkle in ethyl cellulose and agitate until dispersed. Gain 300 F. 5

and oil fire.

Example 34 Santicizer 9 66 Polyvinyl acetate 33 Process.Heat Santicizer 9 to melt. At 280 F. add polyvinyl acetate.

When uniform, take off five. Do not exceed 350 F.

' Example 35 A B C D E Santicizer 9 40 33 25 33. 3 22. 2 Glyceryl monostearate a 40 33 25 22. 2 33. 3 Castor wax (Baker's polymerized castor oil). 25 22.2 22.2 Ethyl cellulose N-14 20 33 25 22.2 22.2

Process.--Heat to melt all ingredients except ethyl cellulose. Gain 280 F. Then with agitation slowly sprinkle. in ethyl cellulose. Continue agitation until ethyl cellulose is uniformly dispersed. Gain 300 F. and off fire.

Example 36 Glyceryl monostearate 25 Santicizer 9 25 Castor wax 25 Polyisobutylene (Vistanex LM-MS, Enjay Co.) 25.

Pr0cess.-Heat glyceryl monostearate, Santicizer 9 and castor wax to around 250 F. Add Vistanex LM-MS and with agitation disperse Vistanex. When uniform, gain 300 F. and off fire.

SOLVENT SYSTEMS Example 37 A B C D E F Glyceryl monostearnte 10 10 10 10 10 10 Vlstanex 13-100 solids) (4. 4) (5. 3) (8. 8) (9. 7) (13. 2) (17.6)

istanex B-IOO. 8.8% sol. in mineral spirits 5O 60 200 Mineral spirits. 40 40 40 40 40 40 Magnesium silicate.-." 12 12 16 16 20 24 Titanium calcium 6 6 8 8 10 12 Process.--Heat glyceryl monostearate to melt.- At 250 F. slowly add Vistanex 3-100 solution. mineral spirits. Then add magnesium silicate and titanium calcium and grind or run through colloid mill.

Example 38 A. B O D E F G Continue agitation until dispersed;

Then add t cul) 70 60 50 40 05 55 45 Prcess.-'Heat glyceryl monostearate to melt. Add

. I TERB M naphtha, stlr untll cool. Grlnd. Dlssolve ethyl cellulose WA ORNE SYSTE S n naphtha. Stir the glyceryl monostearate dispersion mto the ethyl-cellulose solution. Emmi)! A B o D E Example 39 FORMULA I s fil h l l 1 ti g poymel' 8-5 0! B I D I E I F I 1. RhoplexA 33,sollds(Rohm& h l 10 Haas. polyaerylate water emulg 2 Bks 11a"sallaszsnslleeilaly' ylce u se( 14 B0 70 60 50 v 40 30 WetP )1lyviny1 methyl ether 20 so 40 so 60 70 so 3 ffigg gjfig; gg figffilpoly. 8Q

m: l v Y Ethyl cellulose (N44) 157 Y vmyl acetate q Pl? x lel n n n 533 466 400 333 266 200 133 1 l g g gg 20 10 oyvmy H18 y B- (I mtoluonotun 100 150 200 250 300 350 400 g: ifiygg fi gfififiiilii 20 1 7. Gum arabic Wet film: 4 I y 1 Rhoplex, so-sa, 46%. .174 195 174 195 P C S- --DISSOIVC ethyl cellulose 111 xylene. Dlssolvea v polyvinyl methyl ether in toluene. Addthe ethyllcellu- 20 f j I: lose solution to the polyvinyl methyl ether solution. $303393ailgfggsfi gfiaann (Note: A is too thick. Requires more solvent m); 8.51m, 50%, aqueous -IIII l n G H I I Example 50 FORMULA I f i fl 11' l l ll g p0 ymer-p 88 C1 B C D E G 1. Rhoplex lac-33, solids (Rohm & Haas, polyacrylate water emul- Dry film: O ""1' Villyllto VAGH (Bakelite all: figlii gtgglgtffihigh P0P 3. wo-1ao, solids (Bakelite, polyc t g cet te) 80 0 0 0 40. go 20 r vlnylaceme emulsion); g0 90 f gfl n5 Z0 40 50 60 so B. livaltfil'lsenlsltlve adhesion modifier:

'egue Vmyme. VAGH '(Bakehm) 5. Sodium carboxymethyl cellulose m y lsobul'yl '6, Polyvinyl methyl ether 1O ketone) 533 466 400 333 266 200 133 7 Gum mm Polyomide 115 (Gereral Mills) t wet (20% in T01l1er1E) 100 150 200 250 .300 350 400 Rhop'lex A6433 45% 174 195 I Bks. 114, 40% 225 wo-1so 60%; 133 .150 l lu l ifi fifi ny 166* 0 l 0 yv y met y e Ql' aqueous- P r cess Dissolve vmyllte in methyl lsobutyl ketone. Gummbc' 50%3411801; 4o 20 D ssolve polyamlde 1n toluene. Add the polyamlde solu- 40 tion to the vinylite solution slowly with constant stirring. 4

' Example Example 41 A A B C D E F G 45 D y FORMULA a. Latex Bks. 114, 40% (Bakellte's) polystym.. l l Y b R... to l Polyvinyl acetate AYAT so 70 so 5o 4o 30 20 l'fff gfi gi g m 80 c ril 20 0 40 0 0 8 o. Adhesion modifier emulsion, Sauticizer 9 (Monsanto), solidsso- 20 so- 20 15% Folyv nyl acetate 50 w t film;

AYA In lsvpropyll 'a. Latex Bks. 114,407., v50-200 g fi g llt; water, 10% by 5 466 400 666 200 b. Latex Rhoplex A9453, 46%.- "5 35 65. ztlgg u l. Rh 1 3 20% SantlcizerQinCellosol 100 150 20o 250 300 350 400 sanmiwg l v I Santlcizer 9 Emulsion 30% (mlxture ot ortho and para toluene sulionamides).

Process- -Dissolve polyvinyl acetate in a mixture of 90% isopropyl alcohol and 10% water. Dissolve Santicizer' 9 in Cellosolve. Mix the two solutions.

' Processo-Dissolve polyvinyl acetate in ethyl alcoholwater mix (25:1). Dissolve polyamide 115 in toluene. Stir the two solutions together. 1

Pr0cess.-Stir the emulsion to sive beating of air into the mix.

SANTICIZER 9 EMULSION gether, avoiding exces- Santicizer 9 p 15% aqueous sol.Ammonium casein'ate 36 Triethanolamine oleate o..'. 6 1 Water 1 44 (2) Water 200 Process. "Heat Santicizer 9 and (2) 200parts of water to boiling; Add the mixture of ammonium caseinate,

triethanolamine oleate and 1) 44 parts water. Stir vigorously. Grind or run through homogenizer.

Example 45 Resin base: o

v Santicizer 9 (Monsanto) 65.5 Stearie acid 4 i 65.5 Glyceryl monostearate (Aldo 33,'Glyco Co.) 65.5 Ethyl cellulose (N-l4, Hercules) 65.5

v water-sensitive.

11 Emulsion:

Resin base 262 aqueous sol. ammonium cascinate 90 Triethanolamine oleate 8 (1) H O 44 (2) H O I 1,000 ASP 100 filler, 64% aqueous slurry 155 Add more water for application if required.

Process.Resin base to 250 F. Add slowly to mix in Waring Blender of ammonium caseinate, triethanolamine oleate and (1) 44 water. Add ASP 100 slurry and water.

Example 46 Resin base:

Glyceryl monostearate (Aldo 33) 65.5 Santicizer 9 65.5 Ethyl cellulose, Nl4 131.0 Emulsion:

Resin base 262 Cellosolve (ethylene glycol monoethyl ether) 26 15% aqueous solution ammonium caseinate-.. 45 Triethanolamine oleate 8 (1) Water 44 (2) Water 1344 Titanium calcium pigment s. 100 Magnesium silicate extender 200 Pr0cess.-Resin base to 250 F. Add Celosolve. Then add mix slowly to mix in Waring Blendor of ammonium caseinate, triethanolamine oleate, and (l) 44 water. Add titanium calcium and magnesium silicate alternately with remainder of water. Grind or run through homogenizer.

Example 47 FORMULA l Lacquerhase polyvinyl acetate (AYAA) emulsion:

(A) 82% lacquer phase:

Polyvinyl acetate AYAA 50. Tricresylphosphats 5. Toluene. 3. Oleic acid (B) 18% water phase:

Distilled water 28% ammonium hydroxide lacquer-phase emulsion andthe aqueous polyvinyl methyl ether solution. I

Where an excessive degree of contamination is to be encountered, removable undercoatings are used to supplement the composition described above. Thisunderooating may be alkali-sensitive or, like the topcoating, also be In the first instance, after the watersensitive top-coating has been removed by the application of pressured hot water or steam, a mild alkali solution, such as soapy water or hot Weak sodium hydroxide solution, is applied to remove the undercoating along with the balance of contaminants. not carried off by the previouslyremoved top-coating film. In the second instance the topcoating and undercoating are removed together at the 12 pressured hot water or steam application. When the water-sensitive undercoating is used a dual removal action results. The removability of the water-sensitive topcoating is'acceleratcd by the fast loss of adhesion caused by the water-sensitive undercoating giving way. Typical of water-sensitive materials which may be used in the undercoating are methyl cellulose, sodium alginate, and.

polyvinyl methyl ether. The alkali-sensitive coating may employ certain carboxylated polyvinyl acetate polymers such as Shawinigans C3Vl0M or others of this series. A typical formulation for one such alkali-sensitive undercoating is as follows:

Example 48' Parts by weight C3Vl0M polymer (Shawinigan) Butanol 105 Xylol 105 sole alkali-removable coating. composition are the following: I

Example 49 Water base formulation (clear): Parts by weight C3Vl0M polymer resin (Shawinigan) 28% NH OH 3 Water 230 Pine oil 3 Example 50 Water base formulation (clear): Parts by weight I C3Vl0M polymer resin (Shawinigan) 100 28% NH OH Water I 228 Pine oil v 3 Pigments may be addedto Examples 49 and 50 to pro duce camouflage or decorative colors. 7

Various modifications falling within the scope of normal skill in the art obviously may. be resorted to and are contemplated by this invention.

What is claimed is: p

1. A process for protecting surfaces liable to be subjected to contamination which comprises applying to said surfaces, prior to exposure of the surfaces to contamination, a relatively substantial layer of an alkali-sensitive coating composition whose dry film is removable by an alkali-solution in proportion to the degree of alkalinity of the removing solution and washing said alkali-sensitive coating, after exposure of said surfaces to contamination, with an alkali .solution whose alkalinity is adjusted to remove the contaminated portion of the coating but leave.

on the surfaces the uncontaminated portion of the coating. 2. The process of claim 1 wherein the composition of said alkali-sensitive coatingcomprises, by weight, about 29.7% polymer resin, about 0.9% ammonium hydroxide,

about 68.5% water, and about 0.9% pine oil.

3. The process of claim 1 wherein the composition of said alkali-sensitive coating comprises, by weight, about 29.7% polymer resin, about 1.5% ammonium hydroxide, about 67.9% water, and about 0.9% pine oil.

4. An alkali-sensitive protective coating composition whose dry film is removable by an alkali solution in proportion to. the degree of alkalinity of the removing solution comprising, by weight, about 29.7% polymer If such a coating is sutfi l V 1 3,063,878 I 1 V 13 v 14, resin, about 0.9% ammonium hydroxide, about 68.5%; References Cited in theme of this patent water and about 0.9% pine oil. UNITED STATES PATENTS 5. An alkalisensitive protective coating composition whose dry film is removable by an alkali-Solution in pro- 2 93 93 e 13' 19 7 portion to thedegree of alkalinity of the removing solu- 5 2 5 3 537 Mam u 7 1951 tion comprising, by weight, about 29.7% polymer resin, 2 577 5 4 m 4 1951 about 1.5% ammonium hydroxide, about 67.9% water, 377 1 aet 31 0 1959 and about 0.9% pine oil. I 

1. A PROCESS FOR PROTECTING SURFACES LIABLE TO BE SUBJECTED TO CONTAMINATION WHICH COMPRISES APPLYING TO SAID SURFACES, PRIOR TO EXPOSURE OF THE CURFACES TO CONTAIMINATION, A RELATIVELY SUBSTANTIAL LAYER OF AN ALKALI-SENSITIVE COATING COMPOSITION WHOSE DRY FILM IS REMOVABLE BY AN ALKALI SOLUTION IN PROPORTION TO THE DEGREE OF ALKALINITY OF THE REMOVING SOLUTION AND WASHING SADI ALKALI-SENSITIVE COATING, AFTER EXPOSURE OF SAID SURFACES TO CONTAMINATION, WITH AN ALKALI SOLUTION WHOSE ALKALINITY IS ADJUSTED TO REMOVE THE CONTAMINATED PORTION OF THE COATING BUT LEAVE ON THE SURFACES THE UNCONTAMINATED PORTION OF TH COATING. 